Abstract
Characterzation of polyphenolic compounds in the stems of P. multiflorum was conducted using HPLC, high resolution LC-MS and LC-MSn. Proanthocyanidins in particular were isolated in 4.8% yield using solvent extraction followed by Sephadex LH-20 fractionation. HPLC analysis using a diol column revealed oligomers (from dimer to nonamer) as minor components, with (epi)catechin monomeric units predominating, and oligomers with higher degree of polymerization being dominant. Thiolysis treatment of the proanthocyanidins using mercaptoacetic acid produced thioether derivatives of (epi)catechin as the major product and a mean value of the degree of polymerization of 32.6 was estimated from the ratio of terminal and extension units of the (epi)catechin. The isolated proanthocyanidins were shown to strongly inhibit α-amylase with an acarbose equivalence (AE) value of 1,954.7 µmol AE/g and inhibit α-glucosidase with an AE value of 211.1 µmol AE/g.
Highlights
The root of Foti or Polygonum multiflorum Thunb has found broad use as a tonic and herb in China for many traditional uses, including treatment of hair loss [1], replenishing the vital essence of blood, curing malaria, and clearing away toxins [2]
In addition to the radical scavenging activity, Sang and workers have shown that stilbene glucoside from Polygonum multiflorum Thunb can trap methylglyoxal, the toxic reactive carbonyl species that can react with proteins and lead to the formation of advanced glycation endproducts (AGES) [8]
A peak at m/z 451 arises from heterocyclic ring fission (HRF) of the heterocyclic rings; a peak at m/z 425 arises from retro-Diels-Alder fission (RDA-F) of the heterocyclic rings, and, lastly, a peak m/z 287 fragment is formed via quinone-methide (QM) cleavage of the interflavanic bond [11]
Summary
The root of Foti or Polygonum multiflorum Thunb has found broad use as a tonic and herb in China for many traditional uses, including treatment of hair loss [1], replenishing the vital essence of blood, curing malaria, and clearing away toxins [2]. The main active constituents in the roots have been characterized as polyphenolic compounds, including hydroxyanthraquinones, stilbenoids and proanthocyanidins [3,4], which are responsible for the radical scavenging activity of the roots [5]. Thunb roots were mostly extractable using water [7], indicating the active components are hydrophilic compounds including 2,3,5,4'-tetrahydroxystilbene 2-O-β-D-glucopyranoside, which is the main antioxidant in the root [5]. The existing literature on bioactive components strongly substantiates the health promotion effects of the roots of Polygonum multiflorum Thunb. It has been reported that the stem of Polygonum multiflorum Thunb, exhibited even more potent antioxidant capacity than the root of Polygonum multiflorum Thunb [10], its polyphenolic profile is not fully characterized. Using a high throughput assay as a guide, we identified and characterized the proanthocyanidins in the stems as potent starch hydrolase inhibitors, which has potential as functional ingredients in reducing postprandial hyperglycemia
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